In a vehicle, a transmission is provided in a path between an engine and driving wheels to make conversion into a rotational speed and a torque, both corresponding to required characteristics. As such a transmission, there is known a continuously variable transmission wherein a driving pulley comprising a fixed driving pulley piece and a movable driving pulley piece is mounted on a driving shaft, a driven pulley comprising a fixed driving pulley piece and a movable driven pulley piece is mounted on a driven shaft, and a belt is entrained on both the driving pulley and the driven pulley.
FIG. 3 shows a conventional continuously variable transmission. In FIG. 3, the reference numeral 202 denotes an engine, 204 denotes a crank shaft, 206 denotes a continuously variable transmission, 208 a driving shaft, 210 a driven shaft, 212 a driving pulley, 214 a driven pulley, and 216 a belt. In the continuously variable transmission 206, the driving pulley 212 is mounted on the driving shaft 208 which is coaxial with the crank shaft 204 of the engine 202, the driven pulley 214 is mounted on the driven shaft 210 which is disposed in parallel with the driving shaft 208, and the belt 216 is entrained on both driving pulley 212 and driven pulley 214.
The driving pulley 212 comprises a first fixed driving pulley piece 218 fixed onto the driving shaft 208 and a second movable driving pulley piece 220 which is mounted on the driving shaft 208 in an axially movable and non-rotatable manner relative to the shaft 208. The driven pulley 214 comprises a first fixed driven pulley piece 222 fixed onto the driven shaft 210 and a second movable driven pulley piece 224 which is mounted on the driven shaft 210 in an axially movable and non-rotatable manner relative to the shaft 210.
In the continuously variable transmission 206, the driving shaft 208 is rotatably fitted on an input shaft 226 which is coaxial with the crank shaft 204, a forward/reverse change-over mechanism 228 is mounted on the input shaft 226 at a position between an output side/end of the input shaft 226 spaced apart from the engine 202 and an input side/end of the driving shaft 208 spaced apart a longer distance from the engine 202 than the driving pulley 212, an output shaft 230 is rotatably fitted on the driven shaft 210 on an output side/end closer to the engine 202 than the driven pulley 214, an output clutch 232 is disposed between the output side/end of the driven shaft 210 and the input side/end of the output shaft 230, a reduction gear train 236 is disposed between the output shaft 230 and a counter shaft 234 disposed in parallel with the output shaft 230, and a final gear train 242 is disposed between the counter shaft 234 and a differential case 240 of a differential 238 disposed in parallel with the counter shaft 234.
In a continuously variable transmission 306 shown in FIG. 4, a driving pulley 312 comprising a first fixed driving pulley piece 318 and a second movable driving pulley piece 20 is mounted on a driving shaft 308 which is coaxial with a crank shaft 304 of an engine 302, a driven pulley 314 comprising a first fixed driven pulley piece 322 and a second movable driven pulley piece 324 is mounted on a driven shaft 310 disposed in parallel with the driving shaft 308, and a belt 316 is entrained on both driving pulley 312 and driven pulley 314.
In the continuously variable transmission 306, an input shaft 326, which is coaxial with the crank shaft 304 and the driving shaft 308, is mounted on an input side/end of the driving shaft 308 closer to the engine 202 than the driving pulley 312, a torque converter 344 and a forward/reverse change-over mechanism 328 are mounted on the input shaft 326, a reduction gear train 336 is disposed between an output side/end of the driven shaft 310 and a counter shaft 334 disposed in parallel with the driven shaft 310, and a final gear train 342 is disposed between the counter shaft 334 and a differential case 340 of a differential 338 disposed in parallel with the counter shaft 332.
In a continuously variable transmission 406 shown in FIG. 5, a driving pulley 412 comprising a first fixed driving pulley piece 418 and a second movable driving pulley piece 420 is mounted on a driving shaft 408 which is coaxial with a crank shaft 404 of an engine 402, a driven pulley 414 comprising a first fixed driven pulley piece 422 and a second movable driven pulley piece 424 is mounted on a driven shaft 410 disposed in parallel with the driving shaft 408, and a belt 416 is entreained on both driving pulley 412 and driven pulley 414.
In the continuously variable transmission 406, an input shaft 426 coaxial with both crank shaft 404 and driving shaft 408 is disposed on an input side/end of the driving shaft 408 closer to the engine 402 than the driving pulley 412, an electromagnetic clutch 446 and a forward/reverse change-over mechanism 428 are mounted on the input shaft 426, a reduction gear train 436 is disposed between an output side/end of the driven shaft 410 and a counter shaft 434 disposed in parallel with the driven shaft 410, and a final gear train 442 is disposed between the counter shaft 434 and a differential case 440 of a differential 438 disposed in parallel with the counter shaft 434.
In a continuously variable transmission 506 shown in FIG. 6, a driving pulley 512 comprising a first fixed driving pulley piece 518 and a second movable driving pulley piece 520 is mounted on a driving shaft 508 which is coaxial with a crank shaft 504 of an engine 502, a driven pulley 514 comprising a first fixed driven pulley piece 522 and a second movable driven pulley piece 524 is mounted on a driven shaft 510 disposed in parallel with the driving shaft 508, and a belt 516 is entrained on both driving pulley 512 and driven pulley 514.
In the continuously variable transmission 506, an output shaft 530 is rotatably fitted on the driven shaft 510 on an output side/end spaced apart a longer distance from the engine 502 than the driven pulley 514, an output clutch 532 is disposed between an output side/end of the driven shaft 510 and an input side/end of the output shaft 530 spaced apart from the engine 502, a forward/reverse change-over mechanism 528 is disposed between an output side/end of the output shaft 530 close to the engine 502 and an input side/end of a counter shaft 534 spaced apart from the engine 502, the counter shaft 534 being disposed in parallel with the output shaft 530, and a final gear train 542 is disposed between an output side/end of the counter shaft 534 close to the engine 502 and a differential case 540 of a differential 538 disposed in parallel with the counter shaft 534.
In a continuously variable transmission 606 shown in FIG. 7, a driving pulley 612 comprising a first fixed driving pulley piece 618 and a second movable driving pulley piece 620 is mounted on a driving shaft 608 which is coaxial with a crank shaft 604 of an engine 602, a driven pulley 614 comprising a first fixed driven pulley piece 622 and a second movable driven pulley piece 624 is mounted on a driven shaft 610 disposed in parallel with the driving shaft 608, and a belt 616 is entrained on both driving pulley 612 and driven pulley 614.
In the continuously variable transmission 606, an input shaft 626 coaxial with both crank shaft 604 and driving shaft 608 is disposed on an input side/end of the driving shaft 608 closer to the engine 602 than the driving pulley 612, a forward/reverse change-over mechanism 628 is disposed between an output side/end of the input shaft 626 spaced apart from the engine 602 and an input side/end of the driving shaft 608 close to the engine 602, a reduction gear train 636 is disposed between an output side/end of the driven shaft 610 close to the engine 602 and a counter shaft 634 disposed in parallel with the driven shaft 610, and a final gear train 642 is disposed between the counter shaft 634 and a differential case 640 of a differential 638 disposed in parallel with the counter shaft 634.
Continuously variable transmissions of this type are disclosed in Japanese Published Unexamined Patent Application Nos. Hei 8-14344 and Hei 10-196749.
According to the descriptions of these unexamined publications, in a continuously variable transmission wherein a driving pulley comprising a first fixed driving pulley piece and a second movable driving pulley piece is mounted on a driving shaft which is coaxial with a crank shaft of an engine, a driven pulley comprising a first fixed driven pulley piece and a second movable driven pulley piece is mounted on a driven shaft disposed in parallel with the driving shaft, and a belt is entrained on both driving pulley and driven pulley, an input shaft coaxial with both crank shaft and driving shaft is disposed on an input side/end of the driving shaft closer to the engine than the driving pulley, a torque converter and a forward/reverse change-over mechanism are mounted on the said input shaft, a reduction gear train is disposed between the driven shaft and a counter shaft disposed in parallel with the driven shaft, and a final gear train is disposed between the counter shaft and a differential case of a differential disposed in parallel with the counter shaft.
In the conventional continuously variable transmission wherein the forward/reverse change-over mechanism is disposed on an output side/end of the driven shaft with respect to the driven pulley, the forward/reverse change-over mechanism is required to be large-sized for the transfer of an increased engine torque after deceleration with the belt, thus giving rise to the problem that the continuously variable transmission becomes larger in size.
On the other hand, in the continuously variable transmission wherein the forward/reverse change-over mechanism is disposed on an input side/end of the driving shaft, since the engine torque to be transferred is before deceleration with the belt and hence before increase thereof, it is possible to reduce the size of the forward/reverse change-over mechanism and therefore possible to attain the reduction in size of the continuously variable transmission.
Thus, where the forward/reverse change-over mechanism is provided on an input side/end of the driving shaft, it is possible to reduce the size of the continuously variable transmission, but since the driven pulley and driving wheels are directly connected to each other, it is impossible to rotate the driven pulley while the associated vehicle stops, thus making it impossible to change the belt ratio. Besides, in the event of sudden braking, a load is exerted on the belt from the driving wheels through the driven pulley, thus causing damage to the belt. Further, the belt ratio remains in a top condition at the time of sudden braking and it is impossible to change it into a low condition, thus resulting in deterioration of the vehicular starting performance.
Recently, therefore, it has been highly desired to realize a continuously variable transmission which, while ensuring a compact layout, can change speed during stop of the associated vehicle, can protect the belt from a sudden braking load, and can improve the vehicular starting performance.
According to the present invention, in order to eliminate or minimize the above-mentioned drawbacks, there is provided a continuously variable transmission wherein a driving shaft coaxial with a crank shaft of an engine is supported by a transmission case, a driven shaft disposed in parallel with the driving shaft is supported by the transmission case, a driving pulley is mounted on the driving shaft, the driving pulley comprising a first fixed driving pulley piece fixed onto the driving shaft and a second movable driving pulley piece mounted on the driving shaft in an axially movable and unrotatable manner, a driven pulley is mounted on the driven shaft, the driven pulley comprising a first fixed driven pulley piece fixed onto the driven shaft and a second movable driven pulley piece mounted on the driven shaft in an axially movable and unrotatable manner, and a belt is entrained on both the driving pulley and the driven pulley, the continuously variable transmission being characterized in that a torque converter and a forward/reverse change-over mechanism are disposed on an input side/end of the driving shaft with respect to the driving pulley, and an output clutch is disposed on an output side/end of the driven shaft with respect to the driven pulley.
Thus, in the continuously variable transmission of the present invention, a driving pulley comprising a fixed driving pulley piece and a movable driving pulley piece is mounted on a driving shaft, a driven pulley comprising a fixed driven pulley piece and a movable driven pulley piece is mounted on a driven shaft disposed in parallel with the driving shaft, a belt is entrained on both the driving pulley and the driven pulley, and a torque converter and a forward/reverse change-over mechanism are disposed on an input side of the driving shaft with respect to the driving pulley. According to this construction, since the forward/reverse change-over mechanism disposed on an input side/end of the driving shaft transfers the engine torque before deceleration with the belt and hence before increase thereof, it is possible to reduce the size of the same mechanism. Moreover, since an output clutch is disposed on an output side/end of the driven shaft with respect to the driven pulley, the driven pulley and driving wheels are not directly connected with each other, so that, during stop of the associated vehicle, it is possible to rotate the driven pulley and change the belt ratio. Further, in the event of sudden braking, there is no fear of a load being exerted on the belt from the driving wheels through the driven pulley and thus it is possible to change the belt ratio from top to low condition at the time of sudden braking.